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Forum:DNA decay
Article What do you think about this? I think we should give the whole issue of DNA decay a separate article. If we would do that, the article DNA in Amber, DNA in ice, DNA in bones should only discuss the fragments of DNA found in those media, rather than discussing if it is possible. BastionMonk (talk) 15:34, March 24, 2014 (UTC) Half-life in ice see DNA in ice A Fossil Forum critic responded to my argument about the DNA half-life in Antarctic ice with this: "As for your 1.1 million year DNA half-life, you've taken that completely out of context. Those researchers were extracting DNA from bacteria preserved in ice, not eukaryotic organisms! Bacteria store their DNA in a large circular chromosome and in smaller circular DNA molecules called plasmids. Because of these differences in storage, not to mention vastly different cellular environments, bacterial DNA is often more stable than nuclear eukaryotic DNA. You cannot project findings from one onto the other." :I knew that Bidle studied bacterial DNA, but I didn't know that bacteria DNA was more stable than eukaryotic DNA. I'd hate to point fingers at you Bastion, but did you deliberately mislead me into thinking that the half-life of bacterial DNA would apply to dinosaur DNA? Jurassic Park Treasury (talk) 09:01, September 13, 2013 (UTC) ::I can't remember that I ever said that the DNA in frozen dinosaurs also must have a 1.1 million year DNA half-life time. In the article I wrote Bidle and his team concluded that DNA in Antarctic ice has a of ~1.1 million years. If this model is right, there is almost no DNA left after 65 million years. :I didn't talked about dinosaurs here. However, Bidle's results are the only results about DNA decay in artic ice, so (for now) we have no choice but to extrapolate from it. :I remember that you claimed on my wall that Allentofts 500 years half-life time was an absolute rule for DNA decay, like the rate of . Bidle's results (and the comment of the critic) show that time isn't the only (or even main) factor in DNA decay. The shape of the DNA, cell type and temperature all play pivotal roles. :Still, dinosaurs also have . Maybe this DNA would follow the same decay rate as the bacteria. BastionMonk (talk) 09:35, September 13, 2013 (UTC) The Allentoft half-life paper in question Allentoft's entire paper can be read here. Jurassic Park Treasury (talk) 06:00, March 6, 2014 (UTC) Damage mutations One form of ancient DNA damage is base pair mutations. For example, C bases (cytosine) often change to T bases (thymine) during degradation. Assuming there is still dinosaur DNA in bones, the massive age of it could mean that there is none of the original code left, making it useless. For example, a piece of original Triceratops DNA code could have been ATGACCA. However, after 66 million years of degradation, it could have been changed to GCTGATG. This means that the original code would be impossible to retrieve, and therefore permanently lost. Jurassic Park Treasury (talk) 03:57, July 1, 2014 (UTC) :This is often claimed. However, I have never seen an actual observation that Caveman/Neanderthal/Mammoth DNA has more T bases than extant creatures. Researchers always look at the C/G and A/T ratio in chromosome regions. They should have seen this. BastionMonk (talk) 07:52, July 1, 2014 (UTC) ::It has been seen in moa DNA. In this paper, where scientists reconstruct a moa gene, this was written: ::"A number of additional sequence variations were detected between moa sequences, but nearly all of these were from clones and were C > T transitions commonly the result of aDNA damage." :::Nice find! They do not provide a source for this, though. I am so glad to have this article. Now we have some source for the articles. 14:00, July 1, 2014 (UTC) ::Moa bones, of course, are found in a different environment from mammoth remains. However, in most cases, the environments that dinosaurs lived in were more similar to those of the moa (plains and forest) than those of the mammoth (tundra). Jurassic Park Treasury (talk) 08:02, July 1, 2014 (UTC) :Even if this happens, we could identify these mutations by just comparing the code from multiple animals. Mutations are a random process, so unlikely that the same bases will be damaged in different animals. If mutations make a gene nonfunctional, we also could see that while Testing genes. BastionMonk (talk) 07:52, July 1, 2014 (UTC) ::In the Moa article they just get sequences for multiple cells/bone samples. If there are DNA differences between Moa sequences, the C>T differences are likely time-mutations. The others are genuine. They also compare the sequences with extant sequences. If a mutation is within a domain that is very conserved, it is also likely a time-mutation. They also test the paleo-genes in embryos. So, I think this shows that time-mutations don't make potential dino-DNA useless. BastionMonk (talk) 14:00, July 1, 2014 (UTC) References